A cellular network is a kind of dedicated distributed network with wireless radio access, and nowadays, it is widely used in people’s lives. The statistics shows that currently there are 4 billion mobile subscribers in the world, and unquestionably, the cellular network has been playing the main role of energy consumption in ICT (Information and Communications Technology). This chapter discloses the status of energy consumption in the cellular network and introduces energy efficient transmission strategies for accessing a network of cellular networks, especially in cell selection and power control scopes. For future research perspectives, this chapter also introduces the roadmap of smart radio resource management for energy efficient transmission.
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Along with the rapid growing of telecommunication industry, mobile broadband access is expected to lead huge market growth. Nowadays, there are already more than 4 billion mobile phone subscribers in the world (GSMA, 2009; EARTH Project, 2009), which means every two persons in the world will own at least one mobile phone. As for the mobile broadband subscribers, the number will increase to 1.2 billion before 2012 (EARTH Project, 2009). The fast growth of customers also encourages the rapid updates of technologies. In the recent several years, the main body of new technologies like LTE (Long Term Evolution) is finished by specifications, and many operators of various countries are now planning to deploy LTE networks in the coming years. While following the birth of new networks, the number of BSs will increase further. In EARTH Project (2009), the data shows that the rollout of mobile broadband networks such as LTE is expected to take place on top of existing 2G and 3G networks with an increase of at least 25% in the number of base stations in the networks, just as 3G networks were rolled out on top of 2G with a corresponding increase in the number of base stations. Large number of BSs and huge scale of system will definitely lead to more energy consumption and further more CO2 emissions. In fact, the operators are already facing to the problem of high power expense. In David (2009), the situation of energy expense among the total OPEX (Operational Expenditure) for an operator is analyzed, which is illustrated in Figure 1.
Figure 1. Energy expense in network OPEX
For a European operator, the energy expense will take 18% from the total OPEX, and for an Indian operator, it becomes even worse, as the ratio increases to more than 30%. To improve the income, the operators should devote themselves to save more energy, not only for profit, but also for the living environment of human beings.
Nowadays, there are many companies, universities and other research institutions working together to contribute for the energy saving technologies in mobile communications, e.g. the MOBILE VCE (Eamonn, 2009), a three-year project with more than 15 industrial members and 4 universities. They are focusing on the Green Radio architecture and cross-stack protocols for power reduction. The EARTH project (2009) also a three-year project with more than 15 companies and universities. Their targets focus on high capacity and uncompromised QoS (Quality of Service) system with high-energy efficiency. Other projects include ECOsystem (2009), Smart Grid (2010), etc.